From late 2008 to October 2009 Slovenia blocked Croatia's EU accession negotiations over a bilateral border dispute. While an agreement signed by the prime ministers of the two countries on 4 November is likely to resolve the problem, for those interested in the future of EU enlargement in South Eastern Europe a number of pressing questions remain. Why and how did this conflict escalate? What was its real cost to Croatia's accession process? What made an agreement possible? And what would it mean for Slovenia and the EU if Slovenian voters were to reject the deal in a forthcoming referendum?

The dispute also raises more general questions. What should be the EU's policy in future instances of such bilateral disputes and vetoes? How can the EU address the fact that virtually all Yugoslav successor states still have unresolved border issues with at least some of their neighbours (including Croatia, which has them with Bosnia-Herzegovina, Montenegro and Serbia)? How to ensure that future disputes do not escalate? And does this case hold any lessons for dealing with other vetoes, such as those currently affecting Macedonia's (by Greece) and Turkey's (by Cyprus and France) accession process? Can this crisis be turned into an opportunity for the EU in the Balkans?

These questions will be addressed in a forthcoming ESI discussion paper. In the meantime, listen to ESI's Kristof Bender for an 11 minute summary of the background to the dispute:

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